Soft gamma repeaters (SGRs) are neutron stars with ultra-strong magnetic fields, on the order of 1014 G. As the source of the strongest magnetic fields in the universe, they are ideal objects to study the behavior of matter and light in this extreme environment. SGRs emit recurrent short duration, 0.1s, bursts of soft gamma-rays/hard X-rays that are expected to be highly polarized in the 2-10 keV energy range. By measuring the polarization of these bursts we can learn about the strength and configuration of the magnetic fields, the geometry of the emission region and the mass/radius relationship of the neutron star. Using the archival RXTE/PCA data we analyzed ~3 Ms of observations for SGR1806-20 and SGR1900+14. Over 5000 bursts were detected from the sources and each distribution of burst fluence was found to be well fit by a power law with an exponent of 1.60±0.02 for SGR1806-20 and 1.64±0.03 for SGR1900+14. The power law form holds over 4 magnitudes of fluence and the exponents were found to be independent of the level of burst activity. The exponent values suggest that SGR bursts are associated with a self-organized critical system, similar to earthquakes. To measure the polarization of SGR bursts a wide-field-of-view, large area detector is needed. To accomplish this we designed and tested a negative ion time projection chamber (NITPC) X-ray polarimeter which uses nitromethane (CH3NO¬2) as an electronegative gas additive. Utilizing a double gas electron multiplier (GEM) NITPC with CO2+CH3NO2 as a gas mixture we successfully measured gas gains, imaged photoelectron tracks and measured distributions of their length, measured drift velocity of negative ions in various electric fields, and measured modulation from polarized and unpolarized X-ray sources between 3 and 8 keV. Based on the lab instrument results and our SGR burst fluence analysis we propose an instrument appropriately sized for a NASA Small Mission Explorer Mission (SMEX) that would be capable of measuring the polarization of hundreds of bursts from an SGR in a state of high burst activity.

Les mémoires à pont conducteur (CBRAM) sont une option actuellement étudiée pour la prochaine génération de mémoires non volatiles. Le stockage des données est basé sur la commutation de la résistivité entre les états de résistance élevée (HRS) et faible (LRS). Sous polarisation électrique, on suppose qu'un trajet conducteur est créé par la diffusion des ions de l'électrode active dans l'électrolyte solide. Récemment, une attention particulière a été portée sur les dispositifs contenant un élément semi-conducteur tel que le tellure, fonctionnant avec des courants réduits et présentant moins de défaillances de rétention. Dans ces « subquantum CBRAMs », le filament est censé contenir du tellure, ce qui donne une conductance de 1 atome (G₁atom) significativement réduite par rapport aux CBRAMs standard et permettant ainsi un fonctionnement à faible puissance. Dans cette thèse, nous utilisons la spectroscopie de photoélectrons par rayons X (XPS) pour étudier les réactions électrochimiques impliquées dans le mécanisme de commutation des CBRAMs à base de Al₂O ₃ avec des alliages ZrTe et TiTe comme électrode active. Deux méthodes sont utilisées: i) spectroscopie de photoélectrons par rayons X de haute énergie non destructive (HAXPES) pour étudier les interfaces critiques entre l'électrolyte (Al₂O ₃ ) et les électrodes supérieure et inférieure et ii) les faisceaux d'ions à agrégats gazeux (GCIB), une technique de pulvérisation qui conduit à une dégradation plus faible de la structure, avec un profilage en profondeur XPS pour évaluer les distributions des éléments en profondeur. Des mesures ToF-SIMS sont également effectuées pour obtenir des informations complémentaires sur la répartition en profondeur des éléments. Le but de cette thèse est de clarifier le mécanisme de changement de résistance et de comprendre les changements chimiques aux deux interfaces impliquées dans le processus de « forming » sous polarisation positive et négative ainsi que le mécanisme de « reset ». Pour cela, nous avons effectué une comparaison entre le dispositif vierge avec un état formé, i.e. l'échantillon après la première transition entre HRS et LRS et un état reset, i.e. l'échantillon après la première transition entre LRS et HRS.L'analyse du « forming » positif pour les dispositifs ZrTe / Al₂O ₃ a montré une libération de Te liée à l’oxydation de Zr due au piégeage de l'oxygène de l'Al₂O ₃ sous l’effet du champ électrique. D'autre part, pour les dispositifs TiTe / Al₂O ₃, la présence d'une couche importante d'oxyde de titane à l'interface avec l'électrolyte a provoqué une dégradation permanente de la cellule en polarisation positive. Pour le « forming » négatif, nos résultats montrent un mécanisme hybride, à savoir une combinaison de formation de lacunes d'oxygène dans l'oxyde provoquée par la migration de O2- entraîné par le champ électrique vers l'électrode inférieure et la libération de tellure pour former des filaments conducteurs. De plus, les résultats obtenus par profilométrie XPS et ToF-SIMS ont indiqué une possible diffusion de Te dans la couche d'Al₂O ₃. Lors du « reset », il y a une recombinaison partielle des ions oxygène avec les lacunes d'oxygène près de l'interface TiTe / AlAl₂O ₃ avec une perte de Te. Un mécanisme hybride a également été observé sur les dispositifs ZrTe / Al₂O ₃ pendant le « forming » négatif. En tenant compte du rôle important de la migration d'oxygène dans la formation / dissolution des filaments, nous discutons également des résultats obtenus par XPS avec polarisation électrique in- situ (sous ultravide) pour mieux comprendre le rôle de l'oxydation de surface et des interfaces dans la commutation résistive. / Conducting bridging resistive random accessmemories (CBRAMs) are one option currently investigated for the next generation of non volatile memories. Data storage is based on switching the resistivity between high (HRS) and low (LRS) resistance states. Under electrical bias,a conductive path is assumed to be created by ions diffusion from the active electrode into the solid electrolyte. Recently, special attention has been drawn to devices containing an elemental semiconductor such as tellurium, operating with reduced currents and less retention failures. In these subquantum CBRAM cells, the filament is thought to contain tellurium , yielding a 1-atomconductance (G₁atom) significantly reduced compared to standard CBRAMs and thus allowing low power operation. In this thesis, we use X-rayphotoelectron spectroscopy (XPS) to learn about electrochemical reactions involved in the switching mechanism of Al₂O₃ based CBRAMswith ZrTe and TiTe alloys as active electrode. Two methods are used: i) non-destructive Hard X-ray photoelectron spectroscopy (HAXPES) to investigate the critical interfaces between the electrolyte (Al₂O₃) and the top and bottom electrodes and ii) Gas Cluster Ion Beams (GCIB), a sputtering technique that leads to lower structure degradation, combined with XPS depth profiling to evaluate chemical depth distributions. To FSIMS measurements are also performed to get complementary in-depth chemical information.The aim of this thesis is to clarify the driving mechanism and understand the chemical changes at both interfaces involved in the forming process under positive and negative polarization as well as the mechanism of the reset operation. For that,we performed a comparison between as-grown state, i.e. the pristine device with a formed state,i.e. the sample after the first transition between HRS and LRS, and reset state, i.e. the sample after the first transition between LRS and HRS.Conducting bridging resistive random access memories (CBRAMs) are one option currently investigated for the next generation of non-volatile memories. Data storage is based on switching the resistivity between high (HRS) and low (LRS) resistance states. Under electrical bias,a conductive path is assumed to be created byions diffusion from the active electrode into the solid electrolyte. Recently, special attention has been drawn to devices containing an elemental semiconductor such as tellurium, operating with reduced currents and less retention failures. In these subquantum CBRAM cells, the filament is thought to contain tellurium , yielding a 1-atom conductance (G₁atom) significantly reduced compared to standard CBRAMs and thus allowing low power operation. In this thesis, we use X-ray photoelectron spectroscopy (XPS) to learn about electrochemical reactions involved in the switching mechanism of Al₂O₃ based CBRAMs with ZrTe and TiTe alloys as active electrode. Twomethods are used: i) non-destructive Hard X-rayphotoelectron spectroscopy (HAXPES) toinvestigate the critical interfaces between the electrolyte (Al₂O₃) and the top and bottom electrodes and ii) Gas Cluster Ion Beams (GCIB), a sputtering technique that leads to lower structure degradation, combined with XPS depth profiling to evaluate chemical depth distributions. To FSIMS measurements are also performed to get complementary in-depth chemical information.The aim of this thesis is to clarify the driving mechanism and understand the chemical changes at both interfaces involved in the forming process under positive and negative polarization as well as the mechanism of the reset operation. For that,we performed a comparison between as-grown state, i.e. the pristine device with a formed state,i.e. the sample after the first transition between HRS and LRS, and reset state, i.e. the sample after the first transition between LRS and HRS.

In this work ways of preparation of thin epitaxial cerium oxide film on Cu(110) surface were studied. X-ray photoelectron spectroscopy (XPS), X-ray photoelectron difraction (XPD), low energy electron difraction (LEED), ion scattering spectroscopy (ISS) and scanning tunneling microscopy (STM) were used for the characterization of prepared systems. The island structure of CeO2 was prepared by the method of reactive evaporation in oxygen atmosphere. The influence of temperature on the electronic structure and morphology was studied. At the temperature above 550 ˚C partial reduction to Ce2O3 and reordering of the islands to the CeO2(331) structure was observed. The ceria promoted oxidation of copper surface was approved, since the clean c(6x2) reconstruction of the surface was observed at the oxygen exposure 1,5 order of magnitude lower then on Cu(110) alone. The other model system was prepared by cerium evaporation to the oxygen precovered Cu(110) surface. The mix of (2x1) and c(6x2) surface reconstruction was formed by oxygen exposition at 300 ˚C. Cerium was deposited on this surface, also at 300 ˚C. During the following heating to 500 ˚C the formation of epitaxial film Ce2O3(0001) was observed, accompanied by the formation of large hundreds nm long smooth band structures in the [11̄0] direction.

In spite of the failures to find an ultimate theory of unconventional superconductivity, after many years of research the scientific community possesses a considerable store of theoretical knowledge about the problem. Over time, the focus is gradually shifted from finding a theoretical description of an experimentally observed phenomenon to distinguishing between multiple models that offer comparably reasonable descriptions. From the point of view of an experimentalist, this means that any qualitative under-standing of an experimental observation would no longer suffice. Instead, the empha-sis in the experimental research should be shifted to accurate quantification of obser-vations, which becomes possible only if the results available from all the available ex-perimental methods are connected together by the theoretical glue. Among the meth-ods that are to be unified, ARPES plays a central role. The reason for this is that it gives access to the single-particle excitation spectrum of the material as a function of both momentum and energy with very high resolution. Other experimental techniques, such as inelastic neutron scattering (INS), Raman spectroscopy, or the newly estab-lished Fourier-transform scanning tunneling spectroscopy (FT-STS) probe more com-plicated two-particle spectra of the electrons and up to now can not achieve the mo-mentum resolution comparable with that of ARPES. Such reasoning serves as the mo-tivation for the present work, in which some steps are done towards understanding the anomalous effects observed in the single-particle excitation spectra of cuprates and relating the ARPES technique to other experimental methods. First, the electronic properties of BSCCO are considered — the superconducting cuprate most studied by surface-sensitive methods. The recent progress in un-derstanding the electronic structure of this material is reported, focusing mainly on the many-body effects (renormalization) and their manifestation in the ARPES spectra. The main result of this part of the work is a model of the Green’s function that is later used for calculating the two-particle excitation spectrum. Then, the matrix element effects in the photoemission spectra of cuprates are discussed. After a general introduction to the problem, the thesis focuses on the recently discovered anomalous behavior of the ARPES spectra that partially originates from the momentum-dependent photoemission matrix element. The momentum- and excitation energy dependence of the anomalous high-energy dispersion, termed “waterfalls”, is covered in full detail. Understanding the role of the matrix element effects in this phenomenon proves crucial, as they obstruct the view of the underlying excitation spectrum that is of indisputable interest. Finally, the work describes the relation of ARPES with other experimental methods, with the special focus on the INS spectroscopy. For the optimally doped bilayer Bi-based cuprate, the renormalized two-particle correlation function in the superconducting state is calculated from ARPES data within an itinerant model based on the random phase approximation (RPA). The results are compared with the experimental INS data on BSCCO and YBCO. The calculation is based on numerical models for the normal and anomalous Green’s functions fitted to the experimental single-particle spectra. The renormalization is taken into account both in the single-particle Green’s function by means of the self-energy, and in the two-particle correlation function by RPA. Additionally, two other applications of the same approach are briefly sketched: the relation of ARPES to FT-STS, and the nesting properties of Fermi surfaces in two-dimensional charge density wave systems.

The effects of methane (CH4), diborone (B2H6) and nitrogen (N2) concentrations on the structure and photoelectron emission properties of chemical vapor deposition (CVD) polycrystalline diamond films were studied. The diamond films were grown on single-crystal Si substrates using the hot-tungsten filament CVD technique. Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to characterize the different forms of carbon in the films, and the fraction of sp3 carbon to sp3 plus sp2 carbon at the surface of the films, respectively. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the films. The photoelectron emission properties were determined by measuring the energy distributions of photoemitted electrons using ultraviolet photoelectron spectroscopy (UPS), and by measuring the photoelectric current as a function of incident photon energy.

The focus of the following research was to (1) understand the chemistry involved in nitriding an organosilicate glass substrate prior to tantalum deposition, as well as the effect nitrogen incorporation plays on subsequent tantalum deposition and (2) the reduction of a native oxide, the removal of surface contaminants, and the etching of a HgCdTe surface utilizing atomic hydrogen. These studies were investigated utilizing XPS, TEM and AFM. XPS data show that bombardment of an OSG substrate with NH3 and Ar ions results in the removal of carbon species and the incorporation of nitrogen into the surface. Tantalum deposition onto a nitrided OSG surface results in the initial formation of tantalum nitride with continued deposition resulting in the formation of tantalum. This process is a direct method for forming a thin TaN/Ta bilayer for use in micro- and nanoelectronic devices. Exposure to atomic hydrogen is shown to increase the surface roughness of both air exposed and etched samples. XPS results indicate that atomic hydrogen reduces tellurium oxide observed on air exposed samples via first-order kinetics. The removal of surface contaminants is an important step prior to continued device fabrication for optimum device performance. It is shown here that atomic hydrogen effectively removes adsorbed chlorine from the HgCdTe surface.

Supplying the global energy demand through renewable sources has never been as accessible as it is now thanks to developments in technology and infrastructure that have enabled low-cost energy production from sources like wind, solar, and hydroelectric power. However, the challenge of integrating variable renewable energy generators into existing grid infrastructure has driven the demand for efficient and inexpensive energy storage technologies to buffer these intermittent energy supplies. Using electrochemical devices like fuel cells and electrolyzers is an attractive approach for both the long- and short-term storage of energy, where excess energy is used to drive the conversion of low energy reactants into high energy, storable fuels which can be consumed when energy supply is low. These devices rely on highly active electrocatalysts in order to drive these reactions efficiently. However, a major challenge for these technologies lies in developing catalysts at commercial scale without compromising their selectivity or lifetime. Several degradation mechanisms like catalyst particle detachment, dissolution, or surface poisoning by undesired species can quickly diminish the activity and selectivity of a given catalyst, and drive up the costs of electrochemical storage systems. Thus, developing catalysts that balance stability, activity, and selectivity is crucial to improve the economic viability of these energy storage devices. One approach towards mitigating the issues of catalyst stability and activity is through adhering a semi-permeable oxide membrane onto the catalyst surface, creating a structure known as an oxide encapsulated electrocatalyst (OEC). These architectures have previously been shown to improve reaction selectivity, poisoning resistance and nanoparticle stability by improving the adhesion of catalyst nanoparticles, preventing poisoning species from reaching the buried catalytic interface, and controlling the local concentrations of reactants as a means of shifting reaction kinetics. Though earlier studies of OECs have demonstrated a wide array of beneficial properties that encapsulated catalyst architectures offer, they have often been based on highly heterogeneous electrodes and been evaluated across a wide range of conditions, which complicates the identification of the mechanisms that underlie these improvements. Currently, little is understood about the governing mechanisms that influence how oxide overlayers interact with – and ultimately affect – the catalyst surface, as well as alter the reactions occurring at the buried interface. Design rules that relate OEC structure to catalytic performance have the potential to greatly accelerate the understanding and development of such architectures, and would allow for more rational, targeted design of OEC structure in a way that would accelerate their application to new electrocatalytic systems.The aim of this dissertation is therefore to systematically investigate the design space of OEC architectures by using well-defined, model planar electrocatalysts in order to draw clear relationships between the structure, composition, and chemical/physical properties of OECs and the resulting effects they have on electrocatalytic performance. Using planar Pt catalysts encapsulated by a thin, highly tunable carbon-modified silicon oxide (SiOₓCy) overlayers, properties like overlayer thickness, carbon concentration, and density can be specifically adjusted during the room temperature photochemical synthesis procedures used for overlayer fabrication. Similarly, changing the composition of the underlying Pt catalyst while keeping overlayer properties constant can provide insights into how catalyst and overlayer materials interact with and influence the structure of one another. Rigorous materials characterization like X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry, and scanning electron microscopy (SEM) coupled with electroanalytical techniques such as cyclic voltammetry and impedance spectroscopy relates observations in the physical and chemical properties of OECs directly to the electrochemical performance of various probe reactions. In Chapter 3, carbon-free, SiO₂-like overlayers of uniform thicknesses were synthesized using a room temperature, Ultraviolet (UV)-ozone photochemical process that allowed for specific control over the resulting overlayer thicknesses, which ranged between 1.8 nm and 18.0 nm. Two different compositions of the planar catalyst substrate were investigated at all thicknesses. The first catalyst investigated was a 50 nm thick, uniform layer of polycrystalline Pt that displayed bulk properties. The second, thinner catalyst substrate was only 3 nm thick, and contained trace quantities of oxophilic Ti species at the buried interface, which migrated to the surface during electrode fabrication. Ultimately it was found that electrodes based on ultrathin, Ti-doped Pt possesses thinner Pt oxide (PtOₓ) interlayers, while exhibiting reduced permeability for Cu²⁺ and H⁺ compared to the bulk Pt species. Thin layer Pt electrodes also demonstrated enhanced retention of the SiOₓ overlayer during stability testing in 0.5 M H₂SO₄, credited in part to the differences in PtOₓ concentration and structure that form at the buried interface as a result of trace Ti concentrations. These observations lead to the study presented in Chapter 4, which sought to assess the impact of chemical and physical overlayer properties on resulting electrochemistry. Compositions of the SiOₓCy overlayer were altered by restricting the exposure of electrodes to the photochemical UV-ozone curing step during synthesis, which was responsible for removing carbonaceous groups in the overlayer’s precursor. Limiting the length of this step between 15 minutes and 120 minutes yielded overlayer with residual carbon concentrations ranging between 30% and 4%, respectively, and demonstrated markedly different physical and chemical properties that impacted species transport through the overlayer. Specifically, the less dense, carbon-rich SiOₓCy layers restricted the flux of H⁺ to the Pt interface during the hydrogen evolution reaction (HER) under transport limited conditions, but displayed high permeability towards dissolved oxygen species for the oxygen reduction reaction (ORR). By contrast, the denser, carbon free SiOx layers blocked oxygen transport almost entirely, but showed limiting current densities for HER that were comparable to an unencapsulated surface. This is believed to occur from the differing transport mechanisms for H⁺ and O₂ through SiOₓ, where the former diffuses through a Grotthuss-type transport mechanism, and the latter through a solution-diffusion mechanism. The high density SiOₓ layers therefore constrain the flux of O₂ due to its lower free volume compared to the carbon rich overlayers, but has a higher concentration of silanol carrier groups that promote H⁺ transport. These results demonstrated the impact that overlayer compositions can have on modulating the local concentrations of reactants, and motivated the further study of OECs on alcohol oxidation reactions (AORs) in Chapter 5. Using the same approach to control overlayer composition detailed above, SiOₓCy overlayers deposited on Pt thin film electrodes were fabricated and their catalytic performance towards the oxidation of carbon monoxide, formic acid, and C₁-C₄ alcohols were assessed. All SiOₓCy - encapsulated electrodes decreased the overpotentials required to oxidize and remove Pt-bound CO species – a poisoning intermediate for a number of AORs, with the largest reductions seen for the carbon poor, SiO₂-like overlayers through a possible Si-OH mediated removal step. Unexpectedly though, electrodes that had the largest reductions in CO oxidation overpotentials showed the least enhancement for AOR activity for all encapsulated samples. These observations suggest that a different rate determining step may be governing the overall reaction rate on encapsulated electrodes over the potential ranges investigated - most likely bond scission of C-H bonds and/or oxidation of formate-based intermediates. Finally, Chapter 6 presents results obtained from state-of-the-art operando ambient pressure X-ray photoelectron spectroscopy (APXPS) studies, which were used to investigate the behavior of SiOₓ overlayers and ions in solution to understand local interactions and electronic effects that arise under wetted, electrochemical operating conditions. It was found that the choice of electrolyte had a clear impact on the overlayer’s response to different applied potentials. Si 1s spectra of the SiOₓ overlayer taken in K₂SO₄ electrolytes showed a slight positive correlation with applied potential that signified a weak electronic interaction between the SiOₓ and the underlying Pt. However, when the anion was switched to Cl⁻, clear, non-linear correlations between the Si 1s binding energy and potential emerged, suggesting a major change in the local chemical and electronic conditions within the overlayer. Analyzing ion concentrations also showed that overlayers demonstrate different distributions and ion rejection properties based on an ion’s valence and size. The mechanism through which these changes manifest is quite complex, as the layers themselves can introduce numerous perturbations in the system by disrupting the electrochemical double layer, introducing steric confinement at the buried interface, or promoting different reaction pathways. Although continued work will be necessary to better de-convolute these effects and develop optimized, concise design rules, the studies presented in this thesis illustrate the unique opportunity that the application of OECs has towards the future customization of electrocatalysts for a wide range of chemistries and applications.

Two projects are presented here. In the first, metal-cyclopentadienyl bond dissociation energies (BDEs) were measured for seven metallocene ions (Cp2M+, Cp = η5-cyclopentadienyl = c-C5H5, M = Ti, V, Cr, Mn, Fe, Co, Ni) using threshold collision-induced dissociation (TCID) performed in a guided ion beam tandem mass spectrometer. For all seven room temperature metallocene ions, the dominant dissociation pathway was simple Cp loss from the metal. Traces of other fragment ions were also detected, such as C10H10+, C10H8+, C8H8+, C3H3+, H2M+, C3H3M+, C6H6M+, and C7H6M+, depending on the metal center. Statistical modeling of the Cp-loss TCID experimental data, including consideration of energy distributions, multiple collisions, and kinetic shifts, allow the extraction of 0 K [CpM+ - Cp] BDEs. These are found to be 4.95 ± 0.15, 4.02 ± 0.14, 4.22 ± 0.13, 3.51 ± 0.12, 4.26 ± 0.15, 4.57 ± 0.15, and 3.37 ± 0.12 eV for Cp2To+, Cp2V+, Cp2Cr+, Cp2Mn+, Cp2Fe+, Cp2Co+, and Cp2Ni+, respectively. The measured BDE trend is largely in line with arguments based on a simple molecular orbital picture, with the exceptions of a reversal in Cp2Mn+ and Cp2Ni+ BDEs (although within uncertainty), and the exceptional case of titanocene, most likely attributable to its bent structure. The new results presented here are compared to previous literature values and are found to provide a more complete and accurate set of thermochemical parameters. In the second project, imaging photoelectron photoion coincidence (iPEPICO) spectroscopy has been used to determine 0 K appearance energies for the unimolecular dissociation reactions of several energy selected 1-alkyl iodide cations n-CnH2n+1I+ → CnH2n+1+ + I, (n = 2-5). The 0 K appearance energies of the iodine-loss fragment ions were determined to be 9.836 ± 0.010, 9.752 ± 0.010, 9.721 ± 0.010, and 9.684 ± 0.010 eV for n-C3H7I, n-C4H9I, n-C5H11I, and n-C6H13I molecules, respectively. Isomerization of then-alkyl iodide structures into 2-iodo species adds complexity to this study. Using literature adiabatic ionization energies, ionic bond dissociation energies were calculated for the four modeled iodoalkyl cations and it was shown that as the alkyl chain length increases, the carbon-halogen bond strength decreases, supporting the suggestions set forth by inductive effects. In the modeling with statistical energy distributions and rate theory, the role of hindered rotors was also evaluated and no strong experimental evidence was found either way. The heaviest species in the series, heptyl iodide (C7H15I) was also measured via iPEPICO and showed to have a greater complexity of fragmentation than the lighter analogs. Sequential dissociation of the first fragment ion, C7H15+ leads to C4H9+, C5H11+, and C3H7+ ions in competitive dissociation processes, dominated at low energies by the C4H9+ cation.

No description available.

X-ray photoelectron spectroscopy (XPS) is the most widely used surface analysis technique for chemically probing surfaces. Its popularity stems from the large amount of information that can be gathered about the electronic states of the atoms it probes, including core shell information and valence electron information. Simple qualitative analysis (peak identification) can often be performed, but quantitative analysis is a much more complicated process. Although XPS usage has increased dramatically, so has the amount of erroneous analysis observed in the literature. In my thesis, I first present a perspective on how to improve the quality of surface and material data analysis. This chapter focuses on responsible groups, using population biology models and the Prisoner's Dilemma to describe the situation and the potential changes that must be made to counteract error propagation. I quantify errors in XPS data analysis to provide perspective on the gravity of the situation. Over 400 publications in three journals were analyzed. Additionally, another 900 journals were surveyed to determine the quantity of information in the analysis. The parameters include experimental parameters, e.g., the pass energy, peak fitting parameters, the spot size, X-ray source, and the type of spectrometer. I found that over 40% of the publications had significant errors that could potentially change the conclusions of the publication. About 35% of all papers neglected to note the type of spectrometer used, and 85% did not mention the type of software used for analysis. The latter half of this work focuses on XPS peak fitting. I present a broad overview of peak fitting, including how to determine the appropriate background and peak shapes to use, how to quantify XPS data, and how to account for other phenomena associated with photoemission. The line shape chosen for peak fitting is critical, as it is the synthetic shape that is used to model observed physical phenomena. A detailed review on typical line shapes, including the Voigt and pseudo-Voigt functions is presented, along with how to apply them in peak fitting. How and why asymmetric peak shapes are required is also discussed, including which effects cause asymmetry, and if it is inherent to the material or the method of analysis. Finally, a discussion on using constraints to properly model known effects is presented. These efforts were guided by the findings in the former half of this work. The trends presented here are not unique to XPS. Other fields and techniques have similar reproducibility problems. This work discusses possible solutions and what efforts as a community need to be taken to remedy the reproducibility crisis. Additionally, this work includes guides that have original research to improve approaches to XPS analysis, including peak fitting, constraint parameters, and the appropriate use of line shapes.